1. Field of the Invention
The present invention relates to a sheet-supply cassette, and an image recording apparatus, such as a printer, a copier, or a facsimile machine, that includes a sheet-supply cassette.
2. Discussion of Related Art
There has conventionally been known a sheet-supply cassette that is employed by an image recording apparatus such as a printer, a copier, or a facsimile machine and supplies, one by one, a plurality of cut recording sheets each as a recording medium, and there have been many proposals to provide such a sheet-supply cassette that is changeable or adjustable in size so as to accommodate various sorts of recording sheets having different lengths.
For example, Patent Document 1 (Japanese Patent Application Publication No. 2002-154668) discloses a sheet-supply cassette including a main member that is provided on the side of a sheet feeding device that feeds each recording sheet to a recording device; and a slidable member (i.e., an auxiliary member) that is attached to the main member such that the slidable member is extended from, and retracted into, the main member in a direction parallel to a sheet-feed direction in which each recording sheet is fed. The main member has a double-bottom structure including a bottom plate and an upper plate attached to the bottom plate. The slidable member also has a bottom plate that slidably fits in a space present between the bottom and upper plates of the main member. In a gap left between an upper surface of the bottom plate of the slidable member and the upper plate of the main case, there are provided two lock members that lock the sliding movement of the bottom plate of the slidable member. A pair of elongate holes each of which is elongate in the sheet-feed direction and has two waiting holes at lengthwise opposite ends thereof are formed with an appropriate depth in an upper surface of the bottom plate of the main member. Each of the lock members includes an operable portion that projects upward through a rectangular opening formed through the thickness of the upper plate, and a lower projection that is fitable in either one of the two waiting holes of a corresponding one of the elongate holes so as to fix the sliding movement of the slidable member.
In addition, Patent Document 2 (Japanese Patent Application Publication No. 9-110191) discloses a sheet-supply cassette including a main member that has a box-like shape and opens upward, and a slidable member that is slidable relative to the main member so as to be extended from, and retracted into, the main member. The main member has, on a lower surface of a bottom plate thereof, a plurality of engaging bosses that are distant from each other in a sheet-feed direction in which each recording sheet is fed. The slidable member has, on an upper surface of a bottom plate thereof a lock lever whose intermediate portion is connected to the upper surface such that the lock lever is pivotable on a horizontal plane. In addition, the slidable member includes a front wall having a recess in which a horizontal support shaft is provided such that the support shaft supports an operable member that is operable to unlock the lock lever from one of the engaging bosses. A thickened portion as a lower end portion of the operable member is held in contact with an inclined surface formed in one end portion of the lock lever. Thus, when the lower end portion of the operable member is rotated toward the front wall of the slidable member, the lock lever is rotated on the horizontal plane so as to be unlocked from one of the engaging bosses.
However, in each of the sheet-supply cassettes disclosed by the above-indicated two patent documents, many components are needed to lock the sliding movement of the slidable member and, since it is cumbersome to assemble those components, a production cost of the each cassette is inevitably increased.
In addition, the main member disclosed by Patent Document 1 has the double-bottom structure and therefore a step is formed between the upper plate of the main member and the bottom plate of the slidable member when the slidable member is extended. Also, in the sheet-supply cassette disclosed by Patent Document 2, a step is formed between the upper plate of the main member and the bottom plate of the slidable member when the slidable member is extended because the slidable member overlies the main member. Thus, respective trailing-end portions of recording sheets stacked in the main member and the slidable member fall down, at the step, onto the bottom plate of the slidable member. Consequently the recording sheets are bent or wrinkled at the step. The degree of wrinkling increases in the direction toward the lowermost recording sheet. This leads to occurrence of jamming of recording sheets when they are fed to a recording device, or leads to lowering the quality of recording of images on recording sheets.